Physiological and anatomical studies have revealed that the cat's visual system is detrimentally affected by visual deprivation during the early stages of postnatal life. The details of these physiological abnormalities suggest specific perceptual deficits. In particular, the abnormal organization of receptive field characteristics of cells in cat visual cortex suggests the likelihood of abnormalities in the perception of the spatial organization of light. The virtual absence of the Y-class of thalamic (LGNd) visual cells, coupled with these cells receptive field dynamics, suggests the likelihood of abnormalities in the perception of the temporal organization of light. As a direct test of these perceptual predictions and the propaedeutic step toward an analysis of the functional effects of visual deprivation, the present line of inquiry proposes a detailed psychophysical analysis of visual capabilities in binocularly and monocularly deprived cats. Deprived and normal cats will be tested in a simultaneous two choice visual discrimination apparatus. Psychophysical estimates of spatial acuity, spatial orientation sensitivity, and temporal sensitivity (CFF) will be determined at the immediate termination of deprivation and over a post-deprivation period. The influence of subsequent lesions of visual system structures will be evaluated psychophysically. Analysis of perceptual abnormalities as related to known physiological abnormalities will provide important information on (1) the structural and functional consequences of environmentally induced CNS abnormalities and (2) fundamental information on the structure/ function mechanisms of the normal CNS.